1. Field of the Invention
The present invention relates to a fiber optic connector assembly and method employing one or more fiber movement supports disposed around one or more optical fibers to inhibit sharp bending in the one or more optical fibers. The fiber movement support is more rigid than the optical fiber, so the fiber movement support translates force exerted on the optical fiber towards the axis of the optical fiber to inhibit bending.
2. Technical Background
Optical fiber is increasingly being used for a variety of applications, including but not limited to broadband voice, video, and data transmission. Benefits of optical fiber use include extremely wide bandwidth and low noise operation. With the increasing and varied use of optical fibers, it is important to provide efficient methods of interconnecting optical fibers. Fiber optic connectors have been developed for this purpose. It is important that fiber optic connectors not significantly attenuate or alter the transmitted signal. In addition, the fiber optic connector should be relatively rugged and adapted to be connected and disconnected a number of times in order to accommodate changes in the optical fiber transmission path. Because of the skill required in making optical fiber connections and the variances in applications and environments, fiber optic cables carrying one or more optical fibers are typically pre-connectorized with fiber optic connectors by the fiber optic cable manufacturer before the fiber optic cable is deployed.
Fiber optic connectors may be designed to interconnect one or more optical fibers. For example, a duplex fiber optic cable carries two optical fibers for full duplex communications. A duplex fiber optic connector is typically employed to provide a connector for the two optical fibers in a duplex fiber optic cable. An example of a duplex LC fiber optic connector 10 is illustrated in FIG. 1. The duplex LC fiber optic connector 10 provides a connector for two optical fibers (illustrated in FIG. 2) enclosed in a cable jacket 11 of a duplex fiber optic cable 12. Buffered optical fibers 42A, 42B (illustrated in FIG. 2) enclosed in the cable jacket 11 are exposed from the cable jacket 11 on an end portion. Bare optical fibers 13A, 13B contained within the buffered optical fibers are also exposed on respective end portions 15A, 15B (illustrated in FIG. 2) of the buffered optical fibers. The end portions 15A, 15B are inserted through a boot 14. The boot 14 prevents sharp bends from occurring in the duplex fiber optic cable 12 adjacent a connector housing 16 comprised of an upper housing 17 and a lower housing (illustrated as element 36 in FIG. 2). The end portions of the optical fibers exit the boot 14 and enter the connector housing 16 and are inserted into respective fiber optic connector sub-assemblies 18A, 18B supported by the connector housing 16. More specifically, the end portions of the optical fibers are inserted through respective ferrule holder passages defined by ferrule holders 20A, 20B contained inside respective connector sub-assembly housings 21A, 21B, whereby the bare portions of the optical fibers 13A, 13B extend through ferrules 24A, 24B held by the ferrule holders 20A, 20B. In the illustrated example, the fiber optic connector sub-assemblies 18A, 18B are LC fiber optic connector sub-assemblies.
An optical connection may be established with the bare optical fibers 13A, 13B of the duplex fiber optic cable 12 using one or more adapters 26. As illustrated in FIG. 1, two female-to-female LC adapters 26A, 26B are shown; one for connection to each LC connector sub-assembly housing 21A, 21B. Each LC connector sub-assembly housing 21A, 21B contains a lever 28A, 28B (illustrated in FIG. 2) that contains latches 29A, 29B configured to latch into latch orifices 30A, 30B formed in the LC adapters 26A, 26B on a first end 32A, 32B to create a secure fit between the connector sub-assembly housings 21A, 21B and the LC adapters 26A, 26B. This connection can be released by engaging the levers 28A, 28B to release the latches 29A, 29B from the latch orifices 30A, 30B. The connector housing 16 includes a latch release 34 configured to engage and release both latches 29B, 29B with one action. The LC adapters 26A, 26B each define an internal orifice (not shown) configured to receive the ferrules 24A, 24B and align them with complimentary ferrules from optical connectors connected to the opposing end of the LC adapter 26.
FIG. 2 illustrates the duplex LC fiber optic connector 10 of FIG. 1 with the upper housing 17 of the connector housing 16 removed from the lower housing 36. The upper housing 17 and lower housing 36 are molded such that a connector housing passage 38 is formed inside the connector housing 16 when the upper housing 17 and lower housing 36 are attached to each other. A portion of ferrule holders 40A, 40B and buffered optical fibers 42A, 42B from the duplex fiber optic cable 12 are disposed in the connector housing passage 38. To establish a connection between the bare optical fibers 13A, 13B and the duplex LC fiber optic connector 10, the duplex fiber optic cable 12 is inserted through the boot 14 and into a crimp body 44 retained in a crimp body recess 46 defined by the connector housing 16. The crimp body 44 secures the cable jacket 11 in the connector housing passage 38 of the connector housing 16.
The connector housing 16 is designed to separate the buffered optical fibers 42A, 42B from the duplex fiber optic cable 12 into their own individual LC fiber optic connector sub-assemblies 18A, 18B. In this regard, the two buffered optical fibers 42A, 42B, each with exposed bare optical fibers 13A, 13B on their ends, extend through the crimp body 44 and into the ferrule holders 20A, 20B. A portion of the ferrule holders 40A, 40B are retained inside the lower housing 36 in ferrule holder recesses 45A, 45B. The ferrule holders 40A, 40B illustrated in FIG. 2 include indentions 47A, 47B formed in the outer body of the ferrule holders 40A, 40B that are configured to mate with the ferrule holder recesses 45A, 45B. The ferrule holders 20A, 20B extend out from the ferrule holder recesses 45A, 45B from the connector housing 16 into the connector sub-assembly housings 21A, 21B. The upper housing 17 and the lower housing 36 are mated together via protrusions formed by and extending downward on sides of the upper housing 17 that snap fit it into recesses 43 disposed in the lower housing 36. The upper housing 17 and the lower housing 36 also contain alignment features 48 to ensure that the upper housing 17 is placed onto the lower housing 36 in the correct orientation. FIG. 2 also shows a dual adapter 26′ formed by a single housing, as opposed to the individual LC adapters 26A, 26B illustrated in FIG. 1, for establishing an optical connection with the bare optical fibers 13A, 13B.
FIG. 3 illustrates the duplex fiber optic connector assembly of FIG. 2 with one of the fiber optic connector sub-assemblies 18A, 18B inserted into the individual adapter 26A illustrated in FIG. 1. A bend of about 45 degrees is present in buffered optical fiber 42A. The bend is a result of a force exerted back onto the ferrule 24A as a result of connecting adapter 24A to the optical connector sub-assembly 18A. The force exerted on the buffered optical fiber 42A as a result may have been caused by friction of the adapter 26A exerting a force on the ferrule 24A causing a spring (not shown) inside the fiber optic connector sub-assembly 18A to move back. Alternatively, the force exerted on the buffered optical fiber 42A may be caused by differences in spring force between fiber optic connector sub-assemblies mated together through the adapter 26. Bending of an optical fiber, and in particular excess bending of an optical fiber such as illustrated in FIG. 3, results in high insertion loss.
Sharp bending of optical fibers, such as in the buffered optical fiber 42A illustrated in FIG. 3, occurs because the force is exerted on an optical fiber in a direction that is not parallel or substantially parallel with the axis of the fiber optic cable. For example as illustrated in FIG. 3, because the ferrule holders 20A, 20B are aligned along longitudinal axes 49A, 49B, a force exerted by the ferrules 24A, 24A onto the buffered optical fibers 42A, 42B is also directed along the longitudinal axes 49A, 49B. However, longitudinal axes 53A, 53B of the buffered optical fibers 42A, 42B are angled at angle Θ1 with respect to the longitudinal axes 49A, 49B of the ferrule holders 20A, 20B, because the buffered optical fibers 42A, 42B come into the connector housing 16 along a longitudinal axis 50 that is offset from longitudinal axes 49A, 49B. Thus, the force is directed onto the buffered optical fibers 42A, 42B along the longitudinal axes 49A, 49B of the ferrule holders 20A, 20B and at an angle Θ1 with respect to the longitudinal axes 53A, 53B of the buffered optical fibers 42A, 42B. Thus, the force is not an axial force with respect to the buffered optical fibers 42A, 42B, because the force in not directed along or in a plane parallel to the longitudinal axes 53A, 53B of the buffered optical fibers 42A, 42B. This non-axial force causes the buffered optical fibers 42A, 42B to kink or bend instead of the force pushing the buffered optical fibers 42A, 42B towards the longitudinal axes 53A, 53B and back into the duplex fiber optic cable 12.